1. Field of the Invention
This invention relates to processes for treating single-cell materials to yield a product having improved functional properties. More particularly, it relates to a heat treatment of an aqueous yeast slurry in which the yeast is held at a particular temperature for a predetermined period of time. The optimal time-temperature relationship happens to coincide with a segment of the invertase deactivation curve, which makes invertase a convenient indicator for the completion of the heat treatment.
2. Description of the Prior Art
In recent years, a number of different proteinaceous materials have been developed for use as substitutes for the more traditional sources of protein in the human diet. Included among these proteinaceous materials are the single-cell micro-organisms such as fungi, bacteria, and yeasts. They are generally used in small amounts in a variety of food applications, depending upon their individual properties.
For example, spray-dried Candida utilis is a highly nutritious food product which is high in protein, B vitamins, and essential minerals. It is commercially produced by a fermentation process wherein pure ethyl alcohol, nutrients, and water are sterilized and metered into an aseptic fermentation vessel. Active Candida utilis yeast is then added and grown continuously while the fermentor contents, or broth, is continuously withdrawn. The broth is centrifuged to concentrate the yeast cells into a cream having a yeast cell concentration of about 10-20 weight percent. The cream is then pasteurized and spray-dried to a powder form. The resulting powdered yeast is an effective food supplement by itself or when used in combination with other protein sources. Because of the high food value of such a product, there has been continual interest in improving or varying its functional properties in order to make it more acceptable in various food applications.
It has now been discovered that by subjecting single-cell materials to a controlled heat treatment having temperatures of from about 215.degree. to about 300.degree. F., some of the functional properties of the product are improved. In particular, the heat-treated product exhibits improved acid bite suppression which is of particular importance in salad dressings. It also heightens sour cream flavor and increases smooth mouthfeel. In addition, the heat treated product exhibits other functional properties such as fat sparing, fat binding, emulsification and stabilization control, and water binding, and also benefits a variety of food products such as taco seasoning mix, stroganoff sauce, pizza sauce, and others by heightening flavors and reducing ingredients costs.